1. Field of the Invention
The present invention relates to a device for centering and positioning the upper bead of a crude tire disposed horizontally around a bead ring provided centrally of the upper, vertically movable portion of the mold of a tire curing press.
The fundamental requirement to be met when it is desired to obtain a tire preserving a strict geometrical shape during the curing operation, and having faultless beads, is to properly position said beads around bead rings provided in the upper and lower portions of the curing press mold, respectively, before closing the mould and performing the curing operation proper.
2. Description of the Prior Art
The Applicant has already disclosed in a prior U.S. Pat. No. 3,809,423 an automatic loader for tire curing or vulcanizing presses which, in addition to its specific function of loading crude tires into the press mould, is also designed for positively centering and positioning the lower bead of the crude tire around the bead ring disposed in the lower portion of the press mould.
On the other hand, the Applicant also disclosed in a prior British patent No. 1,368,362 a tire curing press of the type comprising a segment assembly disposed in a cavity centrally of the upper portion of the mold, each segment being movable both vertically and radially under the control of a fluid-actuated cylinder or actuator common to all the segments, and an inflatable vulcanizing bladder located centrally of the lower fixed mold portion. In this press the bead ring disposed centrally of the upper portion of the mould is not fastened to said upper portion but adapted to be moved vertically by means of another actuator simultaneously with the first actuator and said segment assembly. Moreover, the ends of said segments are substantially wedge-shaped so that they can catch from underneath the upper bead of the tyre and force fit said bead around the bead ring when said segments are spread radially outwards, as explained in the above-mentioned British Patent No. 1,368,362. However, with this arrangement the segments cannot properly grip the upper bead of the crude tire unless said bead is perfectly centred in relation to the vertical axis of symmetry of the upper mold portion, and said bead lies in a horizontal or substantially horizontal plane. Now crude tires are relatively soft and prone to undergo a distortion when stored. As a result, when a crude tire is laid upon the lower portion of a vulcanizing press its upper bead is generally out of center with respect to the vertical axis of symmetry of the upper portion of the mold, and it lies in most instances in a plane more or less inclined to the horizontal. Therefore, in the above-described arrangement the radially movable segments are not capable of properly positioning the top bead of the crude tire around the bead ring, and in many cases they are definitely precluded from gripping the bead before positioning same around the bead ring. Consequently, the next curing cycle takes place without the upper bead of the tire being properly positioned, and the resulting vulcanized tire is defective or cannot be used safely, and must therefore be rejected.
The same inconvenience is also observed with other conventional curing presses not equipped with the above-mentioned segments and wherein the upper bead ring is secured to the upper portion of the mold in the press. In fact, in these other types of conventional presses the upper portion of the mold is simply lowered upon the crude tire laid beforehand upon the lower portion of the mold and, since the upper bead of the crude tire is generally out of centre in relation to the vertical axis of symmetry of the mold it cannot position itself automatically around the bead ring during the downward movement of the upper mold portion. Then, when the vulcanizing bladder is introduced and inflated within the crude tire, said bladder will push the upper portion of the crude tire against the wall of the upper mold portion without the upper bead of the tire being properly positioned. As a result, a certain permanent distortion of the tire frequently occurs which, upon completion of the vulcanization operation proper, constitutes a major inconvenience.